Coated metal tubular seal



. FIG. I. 2

I i H FIG. 4.

Nov. 26, 1957 NNNNNNNNNNNN.

ATTORNEY.

United States COATED METAL TUBULAR SEAL Adolph Razdow, Montclair, N. .1.Application September 18, 1956, Serial No. 610,454

3 Claims. (Cl. 288-) The present invention relates to a seal and inparticular to such seal adapted for sealing surfaces.

Several different means have been proposed before for the sealing ofsurfaces, for instance for sealing of a container, and among the knownexpedients gaskets have been used in many instances which are placedbetween two mating parts of the container. Other known expedients arerubber O-rings which are placed in specially designed grooves providedin one of the mating surfaces. The use of rubber O-rings is limited,however, because of the restricted temperature range in view of theknown rubber characteristics. Rubber becomes brittle at temperaturesbelow -50 F. and is subjected to chemical changes above a temperature of350 F. Furthermore, rubber O-rings cannot be used at a very highpressure in view of their limited mechanical strength. A furtherlimitation in the use of rubber O-rings for sealing of containers is dueto the fact that many chemicals which are stored in the containersattack the rubber O-rings.

It is, therefore, one object of the present invention to provide a sealwhich avoids all drawbacks experienced in connection with gaskets andwith rubber O-rings.

It is another object of the present invention to provide a seal whichcomprises a comparatively thin metal tube which is filled with a fluid,preferably a gaseous fluid, as for instance nitrogen or helium or amixture of both said gases or any other suitable gas which remains inits gaseous state within a temperature range of 150 F. to 1200 F., saidgas being in the thin metal tube contained under pressure which may havea range from 600 p. s. i. to 1500 p. s. i., preferably however, 1000 p.s. i. pressure, in order to assure resilient characteristics of the thinmetal tube.

In order to bring about a satisfactory and efficient seal, it isrequired that the thin metal tube has intimate contact with the matingsurface of the container to be sealed or of the cover thereof. It is aknown fact that the degree of efficient contact will depend entirely onthe smoothness of the surfaces which are engaged by the thin metal tube.Thus, a high polished finish on the metal surfaces will appreciablycontribute to a more etfective seal, yet a special working of the tubeengaging surfaces to provide a highly polished finish thereon iscomparatively expensive and time consuming. It is also a known fact thateven polished surfaces have still very fine irregularities which are notvisible with the naked eye but appear quite clearly under a microscope.Depending upon the pressure conditions within the container long termleakages cannot be avoided, even if highly polished surfaces areprovided.

It is, therefore, an additional object of the present invention toprovide a thin metal tube which has a coating on the outer surface ofthe thin metal tube, which coating is designed to enter theirregularities on the more or less polished surfaces engaging the thinmetal tube and due to the inner pressure present in the thin metal tubeto penetrate the crevices in the surfaces engaging the thin metal tube.Such coating material may comprise silicon rubber,polytetrafluoroethylene, also known as Teflon, polymers oftrifluorochloroethylene, also known as Kel-F, soft metals, sponge-likemetals or any other suitable material having resilient characteristics.Such coating provided on the thin metal tube eliminates the otherwisenecessary finishing process of the mating surfaces and results ingreater economy in the production of the sealing device. Syntheticmaterials are not suitable where temperatures above 450 F. are involved.For temperatures of a higher range soft or sponge-like metals will bemore appropriate. Thus the choice of the coating material will dependentirely upon the temperature range to which such sealed container issubjected. Any conventional means may be used for the coating step, asfor instance plating, spraying, vaporizing or any other suitableprocess. It has been found that a metal coating stands up very well evenat a temperature of up to 1200 F. without damaging or reducing theefiect of the metal seal. While it is more practical to provide thecoating on the outer face of the metal tube, it is possible to provideas an equivalent those zones of the metal tube engaging surfaces withsuch coating layer, which expedient brings about substantially the sameresult.

It is still another object of the present invention to provide a processfor sealing a thin metal tube which contains a fluid under pressure byproviding an opening in the thin metal tube and inserting said tube intoa container, feeding gas under pressure to the pressure desired in thetube in the container and closing the opening in the thin metal tube byelectrical heating means, thereby closing said opening while equalpressure prevails inside and outside of the thin metal tube, thenreleasing the pressure in the container and removing the thin metal tubetherefrom.

With these and other objects in view which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood in connection with the accompanying drawing, in which:

Figure 1 is a section through a container equipped with a metal seal inaccordance with the present invention;

Fig. 2 is a fragmentary section through a container with anotherembodiment of the metal seal;

Fig. 3 is a cross section through a metal tube of circularconfiguration;

Fig. 4 is a cross section through a metal tube of rectangularconfiguration; and

Fig. 5 is a cross section through a container for closing an opening inthe thin metal tube after a fluid under pressure has been suppliedthereto.

Referring now to the drawing, Fig. l discloses a container 1 having acover 2 secured thereto by means of bolts 3 extending through theflanges 4 of the container and the flanges 5 of the cover, respectively.A groove 6 is provided in the cover 2, though it is to be understoodthat such groove may also be provided in the container, which groove isdisposed at the face '7 of the cover 2 engaging the face 8 of thecontainer 1. A thin metal tube 9 which may be of circular, rectangularor any other suitable cross section is disposed in the groove 6, whichmetal tube 9 contains a fluid 10 and preferably a gaseous fluid, as forinstance helium, nitrogen or a mixture thereof which contains preferablyto nitrogen and 20% to 10% helium or also any other inert gases. Thefluid 10 in the thin tube 9 is subjected to a pressure which rangespreferably from 600 p. s. i. to 1500 p. s. i. The metal tube 9 may bemade of cold rolled steel, stainless steel, copper, Monel or any othersuitable metal and has preferably a thickness of-.001 to .006 inch. Thediameter of the tube 9 of circular cross section, shown in Fig. 2, orthe outer distance of the opposite sides of the tube 9 of rectangularcross section, shown in Fig. 3, is slightly less than the distancebetween the base of the groove 6 and the opposite face 8 of thecontainer 1, so that upon tightening the screw bolts 3 through theflanges 4 and 5 of the container 1 and the cover 2, respectively, thetube 9 or 9' will be slightly compressed and will be pressed against thebase face of the groove 6 and the face 8 of the container 1 with theentire pressure of 600 p. s. i. to 1500 p. s. i. prevailing in the tube9 or 9.

The tube 9 or 9 can easily be manufactured, for in stance by anextrusion process and assumes at first a longitudinal shape, the lengthof which can be cut to the length required in accordance with the lengthof the groove in a container or a cover therefor, which tube can beshaped in accordance with the shape of such groove and the ends or thejoint of the open ends of the tube can be closed either by soldering,brazing, welding or any other suitable process which will be determinedby the temperature range to which the seal is to be subjected.

While a gaseous fluid provides better operative conditions in mostinstances, it is to be understood that a fluid in the liquid state mayalso be used under proper conditions.

In order to supply a fluid under pressure in the tube a filling opening11 must be provided in the tube which upon filling a fluid underpressure into the tube 9 or 9 can be closed again by brazing or anyother suitable means.

It has been found that if the sealing tube 9 or 9 is used withunfinished engaging surfaces, a slight long term leak could not beavoided, particularly if the inner pressure of a container to be sealedis appreciably high. In order to overcome also this difiiculty and toprovide a seal which stands up even under the highest pressure, the tube9 or 9' receives a comparatively thin coating 12 or 12 which is providedon the tube 9 or 9'. The coating may be made of silicon rubber, Teflon,Kel-F, soft metals as copper, silver, gold or a combination of thesemetals or any other suitable material which may be applied either inform of an alloy or by using double layers of two different metals. Thethickness of the coating of rubber will be preferably Within a range of.001 to .025 inch While layers of a thickness range of .0005 to .005inch will suffice. The coating can be applied by any suitable process,such as plating, spraying, electrodepositing, metal vaporizing in vacuoor the like. It has been found of particular advantage to use a spongytype of coating 12 or 12 on the tube 9 or 9, because this type ofcoating is particularly capable to enter the crevices appearing on thesurfaces engaging the tube and a completely perfect seal even underhighest pressure in the container to be sealed has been encountered. Thesame result may be obtained by providing a coating 12 on the facesengaging the outer face of the metal tube, merely by covering a criticalzone of the face 8 of the container, and/or on the opposite base face ofthe groove 6.

Several means are available to inject a fluid under the requiredpressure of 600 p. s. i. to 1500 p. s. i. in the tube. While anyconventional means may be used to achieve this end, the pressure in thetube can be obtained by feeding a small amount of liquid gas at acomparatively low temperature and sealing off the filling opening 11 orby feeding chemicals in their solid state which when heated at once willassume the gaseous state under the pressure required in the tube. Stillanother method is demonstrated in Fig. 5 of the drawing in which acontainer 13 is provided which is equipped witha feeding tube 14 andwhich has also a manometer 15 in operative connection with the container13. Gas to be filled in the tube 9 is fed into the container 13 underthe required pressure of 600 p. s. i. to 1500 p. s. i. .and tube 9 isdisposed in the container 13 which receives the gas present in thecontainer 13 through the filling opening 11. While the gas pressure ismaintained in the container 13 the filling opening 11 is then closed bybrazing or any other suitable means by the use of an electric heatingcoil 16 and upon permitting the cooling of the brazed filling opening 11which brought about a closing thereof, the pressure in the container isreleased and the tube 9 removed therefrom which can then be insertedinto the groove provided in a container to be sealed.

While the endless tube 9 and 9' is described above as a metal tube andthe seal as a metal seal, it is to be understood that any other suitablematerial may be used for the tube and theseal, respectively.

While I have disclosed several embodiments of the present invention, itis to be understood that these embodiments are given by example only andnot in a limiting sense, the scope of the present invention beingdetermined by the objects and the claims.

I claim:

1. A gasket for sealing a container comprising a completely enclosedpressurized metal member having a wall thickness of no more than .006inch and having a coating of soft material adapted to engage a surfaceof said container to be sealed.

2. The gasket, as set forth in claim 1, in which said coating comprisesa material selected from the group consisting of silicon rubber,polytetrafluoroethylene, polymers of trifiuorochloroethylene and softmetals.

3. The gasket, as set forth in claim 1, wherein said pressurized membercontains a fluid which comprises a material selected from the groupconsisting of helium, nitrogen and a mixture of nitrogen and helium.

References Cited in the file of this patent UNITED STATES PATENTS528,820 Stern Nov. 6, 1894 1,965,126 Kojola July 3, 1934 2,6ll,505Winborn et a1. Sept. 23, 1952 2,638,243 Davies May 12, 1953 2,641,381Bertrand June 9, 1953 2,726,006 Brewer et al. Dec. 6, 1955 FOREIGNPATENTS 207,855 Great Britain Dec. 4, 1923 474,238 Great Britain Oct.27, 1937 595,332 France July 13, 1925 696,684 Great Britain Sept. 9,1953 OTHER REFERENCES Engineering Data Metallic O-rings, May 19, 1954,published by: United Aircraft Products, Inc., Box 1035, Dayton, Ohio.Copy in 288/24 in Division 29.

